The movie's story, which borrows from tales of real-life atrocities but is otherwise fictional, involves Rambo reluctantly helping missionaries traverse the wilderness of the Salween River on their way to deliver supplies to camps of war-ravaged refugees.
Rambo has spent the past two decades living in the region as a hermit, one who has shed patriotism, lost his faith and given up on humanity.
"He realizes his entire existence has been for naught," Stallone says. "Peace is an accident, war is natural. Old men start it, young men fight it, everybody in the middle dies, and nobody tells the truth. He says, 'You think God's going to make it all go away? What has he done and changed in the world? He has done nothing. We are an aggressive animal and will never be at peace.' That's how he feels."
When he encounters the human-rights workers, they "somehow touch the last remaining nerve in Rambo's body," Stallone says.
Rambo arrives in theatres on January 25, 2008.